PROJECT ALERT NOTICE (CO) Flooding in Colorado

Date: Sat, 14 Sep 2013 13:39:51 EDT

Summary: Major flooding in the South Platte River Basin in Colorado.

Major flooding continues for a third consecutive day in the South Platte River Basin in Colorado in an area extending from Denver north to the southern Wyoming border, and west into the foothill streams that drain from the Continental Divide. This includes the major river basins of St. Vrain Creek (includes Boulder Creek), and the Big Thompson and Cache La Poudre River Basins that flow into the main stem South Platte River between Denver and Greeley, Colorado. The flooding is a result of up to 13 inches of rain that occurred September 11-13. Water levels remain above flood stage in several foothill and Front Range streams but are beginning to drop today as the rain has stopped. Many communities remain cut off because of extensive road damage or standing water. The area of major flooding is beginning to shift to the main stem South Platte River downstream of Greeley. This reach of the river contains all of the flow from the three major river basins mentioned above. The National Weather Service is reporting that the South Platte River just east of Greeley is currently almost 7 feet above the major flood stage. Over the next few days, the flood crest will travel about 225 miles downstream to the confluence of the South and North Platte Rivers in North Platte, Nebraska.

Today is also the third consecutive day that crews from the Colorado Water Science Center have been measuring flood flows and completing a few gage repairs. The Nebraska Water Science Center will be assisting with flood measurements on the lower South Platte River on Sunday and Monday. Five of 60 USGS streamgages in the South Platte Basin are not reporting data. Of these, repairs are currently underway at one, two cannot be accessed because of road closures, and two are known to have been swept away. There are some gages reporting suspect data but we are unable to visit these gages because of road closures. On Monday the USGS will shift to flagging high water marks at numerous sites in order to conduct indirect surveys of flood peaks.